Service observing circuits



Dec. 17,'1957 F. c. KucHAs ETAL 2,816,955

' SERVICE oBsERvING CIRCUITS Filedmarch 27, 195sD 14 sheets-sheet 1)hv/1 )mm/.L91

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Dec. 17, 1957 F. c. KUcHAs ETAL 2,816,965

SERVICE oBsERvING CIRCUITS FilBd March 27. 1956 14 Sheets-Sheet 2TTOR/VE Y Dec- 175 1957 iF. c. KucHAs x-:TAL 2,816,955

SERVICE OBSERVING CIRCUITS Filed March 27, 1956 bwl UNT.

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SERVICE OBSERVING CIRCUITS Filed March 27, 195e 14 sheets-sheet 4 Dec.17, 1957 F. C. KucHAs Em 2,816,965

SERVICE oBsERvING CIRCUITS Filed March 27, 1956 14 Sheets-Sheet 5/NVENRS L/ E ROSENE ATTORNEY Dec. 17, 1957 14 Sheets-Sheet 6 Filed March27. 1956 ATTORNEY Dec.Y 17, 1957 F. c. KucHAs ETAL 2,816,965

SERVICE osERvINc CIRCUITS 14 Sheets-She et '7 Filed March 27. 1956 S .miA

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SERVICE oBsERvINC CIRCUITS Filed March 27, 195e I 14 sheets-sheet ,9

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SERVICE oBsERvIN'G cxRcUITs 14 Sheets-Sheet 10 Filed March 2'?. 1956/Nl/ENTORS ATTORNEY Dec. 17, 1957 Filed March 27, 1956 F. C. KUCHAS ETAL SERVICE OBSERVING CIRCUITS Fla.

14 Sheets-Sheet 11 /A/l/E/voRs/f- C- KUCHAS W uERose-NE C 21a/ Dec. 17,19557 F. c. KucHAs ETAL 2,816,965

SERVICE oBsERvING CIRCUITS 14 Sheets-Sheet 12 Filed March 27, 1956 C.hf! pa ATTORNEY Dec. 17, 1957 F. c. KUcHAs ETAL 2,816,965

SERVICE oBsERvINC CIRCUITS Filed March 27, 1956 14 Sheets-Sheet l5 h.GP* Ok. n. 6F. Oh

F C. KUCHAS u 5. Ross/VE ATTORNEY /NVE/voRs Dec. 17, 1957 14Sheets-Sheet 14 Filed March 27, 1956A -f-c. KucHAs /Nl/NTORSV- By,5.274%

ATTORNEY SERVICE OBSERVING CIRCUITS Francis C. Kuchas, Manhasset, andVictor E. Rosene, Queens Village, N. Y., assgnors to Bell TelephoneLaboratories, Incorporated, New York, N. Y., a corporation of New YorkApplication March 27, 1956, Serial No. 574,268

17 Claims. (Cl. 179-1752) This invention relates to telephone systemsand has for its object to improve telephone service by facilitating theobservation of such service.

Service observing on subscriber lines appearing both in manual and dialtelephone exchanges has long been practice. With the advent of tollswitching, special means was required for observing on the trunks andcord circuits used with such systems and one such arrangement isdisclosed in V. E. Rosenes prior Patent 2,709,722, January 31, 1955.

A new field for service observing arises when subscribers dial their ownlong distance calls and switching and charging means are partly orwholly automatic. The charging equipment may be located at the oicewhich serves the calling line. Such equipment is known as automaticmessage accounting equipment, usually abbreviated to AMA. On the otherhand, the charging equipment may be located at a central point serving anumber of outlying oces, in which the equipment is known as centralizedautomatic message accounting equipment, usually abbreviated to CAMA. Acertain number of long distance calls would be observed while observingon the subscribers lines but the relative number of such calls to localcalls is so small that an excessive amount of observation would benecessary in order to collect a significant amount of data relating tolong distance calls.

It therefore becomes desirable to observe on the trunkl circuitscarrying long distance calls.

One type of telephone oiiice "provided with charging equipment for localsubscribers is shown in Patent 2,585,904 to A. J. Busch, February 19,1952, the charging equipment being disclosed in more detail in Patent2,599,353 to H. D. Cahill, W. W. Carpenter, and T. L. Dimond, June 3,1952. An arrangement by which an otlice operates charging equipment forsubscribers at auxiliary oiiices is shown in the application of Breed`Cesareo-Germanton-Roberts-Weber-Wingardner, Serial No. 463,102, tiledOctober 19, 1954. The present invention is designed to serve an oiliceof the type shown in the Busch and Cahill et al. patents modified toalso provide centralized charging as disclosed in the application ofBreed et al. In this type of oice, connections are set up under thecontrol of a common control circuit known as a marker. When a call is tobe set up a marker is seized and the identity and class of the callingline and the called line or trunk is registered therein. To obtainaccess to trunks, connectors known as trunk link connectors areoperated.

The service observing equipment of the present arrangement is alsoprovided with a trunk connector and the trunk circuits on whichobservations are to be made are wired permanently to the serviceobserving connector.

In accordance with one feature of the invention, the service observingoperator sets'up a class indication in the service observing connectorof the class of trunk on which observations are to be made and thisclass indication is extended to all markers. When a marker is called into set up a connection, it cheeks the class of the trunk arentI O ice tobe used in that connection against the class indication received fromthe observing connector and if they are the same, renders the serviceobserving equipment effective to extend the trunk to the serviceobserving desk.

Another feature of the invention lies in means effective if the classindications match for causing the marker to transmit the called linedesignation to a register circuit which later controls the transmissionof this number to the observing operator.

A further feature of the invention includes means for preventing therelease of equipment reached over the outgoing trunk after the callingsubscriber disconnects, to give the service observing operator anopportunity to identify toll line signals which may occur.

These and other features of the invention will be more clearlyunderstood from a consideration of the following v description read inconnection with the drawings in which:

' on CAMA trunks such as the trunk of Figs. 1 and 2;

Figs. 5 and 6 show the observing circuit for observing on AMA trunkssuch as that of Fig. 7;

Fig. 7 shows an outgoing AMA trunk;

Figs. 8 to 13 shows the service observing connector, Fig. 8 showing aplurality of trunk frames, Fig. 9 showing frame connecting relays, Fig.10 showing the frame selecting and trunk selecting equipment, Fig. 11showing the trunk connecting relays, Fig. 12 showing a part of theservice observing trunk and associated trunk reduction and trunkidentication circuits, Fig. 13 showing the remainder of the serviceobserving trunk;

Fig. 15 which appears on the same sheet as Fig. 4 shows a part of amarker; and

Fig. 14 shows the complete service observing arrangement in diagrammaticform with the location of Figs. 1 to 13 indicated thereon.

In the drawing the relay contacts are shown detached from the relaywindings, the relay windings are given letter designations, prefixed bythe number of the figure in which the winding appears and the relaycontacts are identified by corresponding designations. Contacts whichare closed when the relay is deenergized are represented by a singleshort line perpendicular to the lines representing the connectingconductors while contacts which are closed when the relay is operatedare represented by a cross or an X at the junction of the connectingconductors.

A brief description will first be given of the general operation of atelephone olice of the type to which the l service observing arrangementapplies. Such an oice may establish local calls, outgoing calls to localodices and incoming calls from other offices. In addition, it may serveas a tandem point connecting an incoming trunk from one otlice with anoutgoing trunk to a third oliice.

Referring to Fig. 14, when'a call originated at the local subscribersubstation 1400, which is to be extended to la distant oice, thedesignation of the wanted line together with the identiiication of thecalling line is registered in the marker 1401. The manner in which thistakes place is completely described in the above-iden=tied Busch patent.The marker then selects a trunk link frame such as frame 1404 having anidle outgoing trunk such as trunk 1402 and operates the trunk linkconnector 1403 having access to the selected trunk link frame 1404,after which the marker selects and connects with the idle trunk 1402.The marker then operates line link connector 1405 having access to theline link frame 1406 at which the calling line 1400 appears, tests foran idle channel over which line 1400 may be connected to trunk,

1402 and completes a connection between the line and the trunk. Whilethe marker is selecting an idle trunk it also selects an idle outgoingsender such .as sender 1407, operates the outgoing sender connector1408, transmits the calling line identity and the called linedesignation to the outgoing sender and operates the the outgoing senderlink 1409 to connect sender 1407 with trunk 1402. When this connectionhas been completed and the marker has checked that all of the necessaryinformation has been passed to the sender, the marker operates anadvance relay in the sender and releases. The outgoing sender 1407 thenoperates the transverter connector 1410 to initiate the initial entry bythe charging equipment. This equipment is the same as that disclosed inthe above-identified Cahill et al. patent and has therefore not beenshown. The outgoing sender 1409 controls the completion of theconnection and then releases.

If a call is originated at substation 1411 appearing at an auxiliaryoiiice such as the step-by-step oflice 1412, either for a subscriber atthe main office such as the subscriber at substation 1400 or for asubscriber at some other auxiliary oice reached through the main oilice,the substation 1411 will be extended through the oflice 1412 and anoutgoing trunk 1413 at that oice to an incoming trunk at the main oicesuch as trunk 1414. When trunk 1414 is seized it operates the incomingregister link 1415 to connect with an idle incoming register such asregister 1416. The designation of the wanted subscriber is transmittedfrom the auxiliary otlce 1412 to the incoming register 1416. When theregistration has been received, register 1416 operates the incomingregister marker connector 1417 to connect with an idle marker 1401. Assoon as the marker is seized by an incoming register, it operates thesender connector 1408 to select an outgoing sender equipped for CAMA,such as sender 1418, and passes to it the identity of the incoming trunkand the designation of the wanted line. The marker also connects sender1418 through the outgoing sender link 1419 with the incoming trunk 1414.In addition, the marker operates switches on the line link frame 1406and the trunk link frame 1404 to connect the incoming trunk either witha substation such as substation 1400, using the trunk link appearance ofthe incoming trunk 1414, or with the outgoing trunk 1420, using the linelink appearance of the incoming trunk 1414, according to the designationregistered therein. When the marker indicates to the sender 1418 that itis ready to release, the sender 1418 is connected through the outgoingsender link 1419 and the trunk 1414 with the calling substation. Thesender 1418 operates position link 1421 to select an operator at thecentralized operators position 1422. The operator then asks the callingsubscriber for his designation and registers the number in the sender1418 by operating a key set at her position. The sender 1418 thenoperates the transverter connector 1410 tto cause the proper chargingentry to be made. If the call is for substation 1400, the sender 1418now releases. call is for a subscriber reached over trunk 1420, thesender 1418 transmits all or a part of the designation to the distantoice and then releases.

-Service observing desk 1423 may be located at the main ofiice or may belocated at some other oice. The desk 1423 is connected with the serviceobserving circuits by means of the trunk 1424 including three pairsofcouductors over which signaling and monitoring may take place. Thisdesk is essentially the same as that disclosed in the above-identiedRosene patent. The desk may observe on either locally originated callsor on calls originated `at an auxiliary oice but can observe on only onetype of call at a time. Means are provided at the desk 1423 to indicateto the control circuit 1425 what type of calls are to be observed andwhether there is a position at the desk waiting for a call. According tothe type of call to be observed, the control circuit 1425 renders eitherthe local observing circuit (AMA) 17426 or the central# If the i izedobserving circuit (CAMA) 1427 effective. It also indicates to allmarkers what observations are being made and directs the connection oftrunks of the proper type to the effective service observing circuit.The called number is obtained from the marker which'is connected to theservice observing register 1428 by means of the service observingregister connector 1429 under the control of either service observingcircuit when a call is to be observed. Later the register 1428 transmitsthe number to the desk 1423.

OPERATION OF TRUNK CIRCUITS CAMA trunk When the incoming trunk circuitof Figs. l and 2 is seized at the distant oice, a loop circuit is closedwhich may be traced from ground through the left winding of relay l-AE,back contacts of relay 1RV and l-MB, tip conductor 100 of the incomingtrunk, loop circuit at the originating oiiice, ring conductor 101, backcontacts of relays 1-MB and l-RV to battery through the right winding ofrelay 1-AE. Relay l-AE operates in this circuit and closes a circuitfrom battery, front contact of relay l-AE, winding of relay 2-B toground over the back contact of relay l-RC or the back contact of relay1CH. It also closes a circuit from battery over the front contact ofrelay l-AE, back contacts of relays 2-BY, 2-R and 2-D to the startconductor 200 of the incoming register link to initiate the connectionof the trunk circuit with an incoming register. Relay l-AE also connectsground over its front contact to conductors 201 and 202 to prepare fortransmitting the designation as received from the calling oice to thesender, conductor 201 extending over a temporary by-link and conductor202 forming one side of the usual pulsing circuit which extends lthroughthe link switch when the link operation is completed.

Relay 2-B connects battery over a front contact of relay 2-B through theresistor 2BR to conductor 203 forming the other side of the pulsingcircuit. Relay 2-B also connects ground to conductor 224 leading towardsthe service observing control circuit, the purpose of which l lwillappear hereinafter.

As soon as the by-link is closed, the link circuit connects battery toconductor 204 and ground to conductor 20S, completing a circuit throughthe left winding of relay 2-R over a back contact of relay 2-BY,operating relay 2-R. Relay 2-R closes a holding circuit for itself fromground through its right winding to battery over conductor 203. Withrelay 2-R operated, the start conductor 200 is connected over a backcontact of relay 2D, front contact of relay 2-R, and back contact ofrelay 2-BY to battery over conductor 204 and is disconnected from thebattery supplied as previously traced over the front contact of relayl-AE. When the link switch has operated, conductors 202, 203, 206 and207 are connected directly to the selected incoming register. Relay l-AEresponds to the digits pulsed over the incoming trunk and repeats thepulses over conductor 201 or conductor 202 to the incoming register.

When the register has received the complete designation, it connectsground to conductor 206, completing a circuit for operating relay 2-Dwhich connects the incoming conductors and 101 through to the talkingcondensers l-T and l-R. Relay 2-D closes a locking circuit for itselfover front contacts of relays 2-D and 2-R. When relay 2-D operates, itcloses a circuit from ground over a back contact of relay l-CH, backcontact of relay l-RC, front contact of relay 2-D to battery through theWinding of relay 1-RV. Relay l-RV, in operating, reverses the connectionof battery and ground to conductors 100 and 101 which would serve as astart-dial signal if the trunk had been seized by an operator or adistant sender.

With relay 2-D operated, ground is connected through resistor 1-A toconductor 117 to supply ground for holding the switches to be includedin the connection. .Relay 2D also prepares'a number of other circuitswhich will be traced when they are completed. j After the incomingregister has'received the designation, it calls in a marker to which itpasses the called line designation, and the marker determines from thedesignation whether a local subscriber or a distant subscriber is wantedand recognizes that the call is one requiring message billing. Themarker therefore selects a special sender equipped for messageaccounting, prepares the outgoing sender link, and connects battery toconductor 207 operating relays 2LF and 2-TF. Relay 2-LF connectsconductors 208 and 209 together to operate the hold magnet individual tothe trunk in the sender link, the hold magnet remaining operated underthe control of the special sender. The marker passes the called linedesignation to the special sender and disconnects. The special sendercalls in an operator whose position is connected over conductors'213 and214, condensers 1-I and l-K, condensers 1-T and l-R, front contacts ofrelay 2D, front contacts of relay 1-RV, and back contacts of relay 1-MBto conductors 100 and 101 and thence to the calling line. The callingsubscriber is asked for his line designation and the operator registersthe number given in the special sender.

' The special sender then connects ground to conductor 210, completing acircuit over a back contact of relay 2TC to conductor 211 to cause theaccounting equipment to make the initial entry. When the initial entryhas been completed, the accounting equipment connects ground toconductor 212 completing a circuit from battery through resistor 2-GA,winding of relay 2TC, back contact of relay 2TC to ground on conductor212, operating relay 2TC. Relay 2TC locks over its own front contact anda front contact of relay 2D to ground.

After the initial entry has been made by the billing equipment, thespecial sender controls the completion of the connection, using anothermarker. For a local termination relays 2-LF and 2TF are again operatedwhen the marker seizes the trunk link connector. With relay 2-LFoperated, battery through resistor 1D is connected over a front contactof relay Z-LF to conductor 104 to operate a relay individual to thetrunk on the trunk link frame. The marker controls the ringing selectionswitch, rst grounding conductor 105 to complete a circuit over a frontcontact of relay 2-LF to battery through the Winding of relay 1-RC.Relay 1-RC operates and closes a locking circuit for itself over a backcontact of the charging relay l-CH, front contact of relay 1-RC, backcontact of the ringing trip relay l-RT, conductor 106, and through theringing selection switch to ground supplied over a front contact ofrelay 2D and conductor 107. With relay l-RC operated, the markercompletes a circuit over conductor 108, front contact of relay 1-RC,front contact of relay 2-LF, front contact of relay 2D rent, which isconnected throughthewinding of relay 1-RT to conductors 112 and 113 bythe ringing selection switchis extended over front contacts of relaysl-PU and 1-RC to conductors 114 and 115 leading toward the called line.When the called subscriber answers, relayl-RT operates, releasing relayl-RC. With relay l-RC released, conductors 114 and 115 are extended tothe wind-` ings of relay 16 causing that relay to operate.

When relay 2D operated, circuits were prepared for the timing tubel-CHT. Positive battery is normally connected to the main anode of thetube l-CHT and is connected through resistors 1-D and 1-E to condenser1-B and ground. With relay 2D operated, condenser 1-B is connected tothe control anode of tube l-CHT and the upper winding of relay l-CH isincluded in a circuit extending from the cathode of tube l-CHT, frontcontact of relay 2D, upper winding of relay l-CH, back contact of relay1-CH, front contact of relay 2-B, back contact of relay 2TF, frontcontact of relay 2D to ground. Until relay 1S operates, ground isconnected over a back contact of relay 1-S, back contact of relay 2-T,anda back contact of relay l-CH to resistor l-E in shunt of the positivebattery through resistor 1-D. When vrelay 1-S operates, this shunt isopened and condenser l-B charges. When this charge reaches the breakdownpotential of tube l-CHT, the tube breaks down and relay to conductor 110to operate the hold magnet ot the ringing selection switch.

When relay l-RC operates at this time, the circuit of relay l-RV isopened and the connection of battery and ground to conductors 100 and101 is restored to normal.

Relay 1-CH, in operatingas later described, holds the circuit of relay1-RV open.

When the ringing selection switch has been operated, the markerreleases, in turn releasing relays Z-TF and 2LF leaving the hold magnetof the ringing selection switch held over conductor 110, front contactof relay 2D, back contact of relay Z-LF, conductors 106 and 107 toground over a front contact of relay 2D. The ringing selection switch atthe beginning of the ringing cycle connects ground to conductor 111completing a circuit over afront contact of relay l-RC, back contact ofrelay l-CH, front contact of relay 2D to battery f through the Windingof relay 1-PU. Relay 1PU operates and locks over one of its frontcontacts and front contact of relay 2D- to'ground. With relay l-PUoperated, ringing curl-CH operates. Relay l-CH locks in a circuit frombattery through its lower winding overits own front contact, a frontcontact of relay 2-B, back contact of relay Z-TF, front contact of relay2D, and ground, opening at i-ts back contact the circuit through itsupper winding to quench the tube l-CHT.

With relay 1-CH operated, ground supplied to conductor 109 from theringing selection switch completes a circuit over a front contact ofrelay 1CH, front contact of relay 2TC, winding of relay 2MA to batterythrough resistor 2GB. Relay 2-MA operates and locks to ground over itsown front contact. With relay Z-MA operated, conductor 215 is connectedover a front contact of relay 2-MA and a front contact of relay 2TC toconductor 211 to initiate the operation of the accounting equipment tomake the answer entry. When the answer entry has been completed, theaccounting equipment connects ground to conductor 216 which extends overa back contact of relay l-RC, front contact of relay 2D, front contactof relay 2-MA, front contact of relay 2TC to battery through resistorZ-GA in shunt of the winding of relay 2TC causing relay v2TC to releaseto indicate that the answer entry has been completed.

When the calling subscriber releases, relay I-AE'releases, in turnreleasing relays Z-B, 2R and 2D. With relay 2D released, conductors 211and 215 are connected together over a front contact of relay 2-MA and aback contact of relay 24D to initiate the disconnect entry. At the endof the disconnect entry, ground is connected to conductor 216 which isextended at this time over a back contact of relay le-RC, back contactof relay 2D and a front contact of relay 2-MA to battery throughresistor 2-GB in shunt of the Winding of relay 2-MA causing relay 2-MAto release.

If the called substation disconnects rst, the disconnect entry isdelayed. The release of relay 1-S closes a circuit from ground over aback contact of relay l-S, back con, tact of relay 2-T, front contact ofrelay 2D, front con# tact of relay l-CH through the heater winding ofthermostatic relay l-RL. After an interval, relay 1-RL closes itscontact completing a circuit from ground over the contact of relay l-RL,front contact of relay 2-MA to v battery through the winding of relayl-RC. Relay l-RC operates and locks to ground over its own front contactin lparallel with the contact of relay I-RL and, with relay 1-RCoperated, conductors 211and 215 are connected together to initiate aydisconnect entry as previously 1de; scribed. With relay l-RC operated,ground is connected to conductor 222` leading to the accountingequipment :tempes 7 to indicate that the disconnect entry has beendelayed. When'fthe disconnect `entry is `|completeclrelay 2MA is shuntedandreleased,.openingfthe locking circuit for relay 1R`C, permitting that.relay to release. Relay -1-RC,` in operating, disconnects conductors114 and 115 from the windings of relay `l-Scausing that relay torelease, and in turn, release `relay 1CH. With relays l-S and l-CHreleased, the circuit for relay `1--RL is opened and that relay opensits contacts. However the switches Iare not released vuntil .bothsubscribers havedisconnected or until a time .interval felapsesfollowing disconnect by the calling subscriber, `since ,ground isconnected -to conductors 117 and .217 over afront contact of relay 2Dwhich is held operated under'thecontrolof the callingline and overaback-contact of relay I1-RCand a front contact of relay l-CH.Relay1CI-I, isnormally heldoperated under the control of thecallingline, but is also' held operated ,inafcirenit from battery through itslower winding andoven its own frontcontac back contact of relay 2-B andfront contact of relay 1 -S` if the called line holds after the callingline ldisconnects. Under this condition ground is-also connected overk afront` contact of relay 1-S, back contact of relay Z-D, front'contact ofrelay 1CH vtothe heater winding of thermostatic relay 1RL. Relay `1-RLoperates relay l-RC asaabove described, releasing relays `l-S and l-CHand disconnecting .ground from conductors 117- and 217.

If the call is to be Iextended through the main office to anotheroilice, the marker obtains access to the trunk over the line klinktermination shown in Fig. 2, connecting ground to conductor`217during-the time that relay 2-TF is operatedgto operate relay l-TS. Afterrelay 2-TF is released, relay l-TSrernains operated in a circuit frombattery through its winding, yback contact of relay Z-TF, front contactof relay l-TS, front contact of relay 2-D to ground. In addition,l-relay ZY-TF, whilel operated, closes a circuit'throu'gh the winding ofrelay 2TF1 operating the latter relay. Relay `l--TS closes a biasingcir- `cuit through the lower winding of supervisory relay 2-SV. Relayl-TS also disconnects the incoming talking circuit from conductors 114and 115 leading to the trunk link frame and connects them overconductors 118 and 119 and back contacts of relays 2-TB and Z-T to theleft windings of repeating coil y2-A. When the marker has completed itsoperations and releases relay 2TF, the upper winding of relay 2SV isconnected through the right windings of repeating coil 2A overconductors 218 and 219 and the link` switches to the outgoing trunk.Relay 2TF, in releasing, opens the circuit of relay 2-TF1 which is slowto release and ytion of relay 2T in response to the initial oit-hooksignal provided by the intertoll trunk.

The initial entry is made, as previously described, resulting in theoperation of relay 2-TC. When relay 2SV operates in response to ananswer by the called subscriber, a circuit is closed from ground overthe front contact of relay 1-TS, front contact of relay 2SV, backcontact of relay 2-TF1 to battery through the winding of relay 2-T.Relay 2-T operates and closes a circuit from ground over a back contactof relay L-CH, front contact of relay 1-TS, front contact of relay 2-Tto battery through the winding of relay 2-TA. Relay Z-TA operates inthis circuit and locks over a front contact of relay l2TA, front contactof relay l-TS, back contact of relay 1-CH to ground. With relay 2-Toperated, the talking circuit remains dependent upon back contacts ofrelay 2-TB. With relay 2-T operated, the shunt around condenser l-B isopened and tube l-CHT functions to operate relay 1-`CH as abovedescribed. Relay 1-CH operates relay 2-MA, as before, to initiate theanswer entry which is followed. by the release of relay Z-TC.

When the called subscriber disconnects, relay 2SV releases, in turnreleasing relay 2,-T. Release by the calling subscriber releases relaysLAE and 2B to initiate the dis'connect'entry as above described. Therelease of thereby prevents the operarelay I2-T closes a circuitllffol-` 'ground over a b'acli eoflifA fact if relay 1-CH, front Contact of:Mayr-rs back contactV of relay 2T, frntfcontact of freI'a'ylZ-TAl tob't-erythiugh the Winding f relay y2TB. -Re'layJZTB operates inffthiscircuit and disconnects the repeatingcoil Z-A 'from/the incoming endo'f'the trunk. If the calling subscriber ldelays disconnection, therelease of relay 2-T closes the previously traced `'circuit foroperating thermostaticrelay 1-RL whichA functions as above to cause thedisconnect entry 'to'beinade When'both subscribers have disconnectedrelay 'l-'TS releases and restores the trunk to its normal condition. y

Whenthegina'rker 'iirstrperaftes the relay r2lTF, vground. is connectedto conductor 220 leading tothe serviceobserving connector ofFig's. 8 to1,3 to initiaterconnection of the ltrunk with the `seivice-Aobserving.equipment. When 'the connector selects this trunk for kobservation andconnectsitvt'hrough to the equipment, branchesuof.y conductors 213and.214 as well as the conductorsk 224 and 221 are connected to theservice observingcircuit.

It may be noted that-the special outgoingsender and the CAMA operatorare yused for local isubscribers on party lines having morethan twoparties. .,For suchV calls, a junctor circuit is used which connects Vanoutgoing appearance on the trunk link `frame with an incoming appearanceon :the line linie-framek of the same ofhce unit or on the line-.link.frame of second oilice unit, thecall being completed-over a simpleoutgoing trunk. These junctors are also observed, but Vfor simplicity-have not been illustrated in detail.

AM trunk The outgoing trunk` of Fig; 7'1a`ppea's on the trunk linkframe. When the trunky is'idl'e, itcon'nects ground to conjducton700over-back contacts'ofrelys'T-D, 7-MA, 7-TM and,7-S1. 'lher'markeruses/this conductor to select-amiche trunk -linkrframefhavingan:idletrunk of the desiredroute.V Conductors 701 and 702 arelalso connectedtogether whentheftrtmlcisidle iover back contacts of relays 7-'D, LMA,PTM/7451 and the winding-of relay 7-F. The marker usesthese conductorsto test foran idle `trunk a'fter having selected the trunk frame,connectingground-'to conductor 702-and a tes't relay to conductor 70-1.When this trunk is selected'to be used, low resistance battery is'conectedto conductor 701 operating relay 7&1?. Relay 75l?,y inoperating, locks to conductor 702indepc'nde'nt of 'relays 7-S1, etc.Relay 7-F also connects'ground over back contacts of relays 7-CS, 7LGH,'l-TC n'd -the front contact of relay 7-F to 'conductor 703 lto operatea relay individual to the trunk-on` the trunk 4link `frarn'eto Vgive themarker access to' the trunk and to the outgoing connection. With relay7-F operated, the control circuits for the timing tube 7LGHTareopened toprevent false charge. At the same time that the above operations aretaking place, the marker selects an idle outgoing sender and prepares acircuitfor operating the -sender link. With relay 7-Foperated-,,eohductors 7b4-and 705are connected together to operate thehold magnet of the sender link, the hold magnet remainingoperated.underthe control of the outgoing sender. When the trunk has been connectedwith theI sender; the sender connectsgi'ound to conductor 706 completing.a rcircuit through the fright winding of relay 7-D, operatingthatrelay. Relay 7"'-D disconnects the outgoing tip and ring conductors707and 708 from the trunk circuit. Branches of condctorsi707 and 708 extendover conductors 725 and m6-through the sender link to the sender sovthat the sender can signalY the distant oice as required to set up theconnectioninfthat oliice.

With relay 7-D operated, groundc'orinected to c011- ductor 711 bythe'marker is extended overy aifr'ont' contact of relay 7-Ffront contactof relay 7lD`, back contact of relay 7CH, front contact of relay 7LD'vto battery through the windingofrelay 7' 1; Relay 7-Sl operates andconnects ground through resistor 7-A to conductor 712 to hold the linelink and trunk link frames after the trunk link connector circuit hasbeen released.

Relay 761, in operating, closes an operating circuit for relay 762, andthat relay operates, locking over its own front contact, back contact ofrelay 7-CH, front contact of relay 7-D to ground.

When the marker has completed its functions, it releases relay 7-F, inturn releasing the trunk link relay, causing the subscribers line to beconnected to conductors 709 and 710 and completing a circuit over backcontacts of relay 7-TM through the windings of relay 76, to

ground and battery. Conductor 712 is extended to the hold magnets of theestablished connection. Relay 76 operates in series with the callingline, completing a holding circuit for relay 761 which may be tracedfrom battery through the winding of relay 761, front contact of relay7-D, back contact of relay 7CH, front contact of relay 76, front contactof relay 761 to ground. Relay 761 is slow to release to hold over thetime between the removal of ground from conductor '711 by the markerjand the operation of relay 7-S over the subscribers line.

When the marker has disconnected, the sender causes lthe initial entryto be made, connecting ground to conductor 718 which extends over a backcontact of relay 7TM, back contact of relay 7-F, back contact of relay7-TC to conductor 713 leading to the AMA equipment. When the initialentry has been made, the AMA equipment connects ground to conductor 714,completing a circuit over a back contact of relay 7-TC through thewinding of relay 7-TC to battery through resistor 7-GB. .Relay 7-TCoperates and locks over one of its front contacts and the front contactsof relays 761 and 762 to ground. When the initial entry has beencompleted, the outgoing sender is released. The sender, in releasing,releases relay 7-D extending the trunk conductors 707 4and 708 over backcontacts of relay 7-TT, back con- ,operated over the back contact ofrelay 7-D to ground over the front contacts of relays 76 and 761.

When relay 7-F released and relay 762 operated, the circuit for relay7-CH was prepared. High voltage positive battery is normally connectedto the main anode of tube 7-CHT. The control cathode is connected over a-back contact of relay LF, front contact of relay 762, condenser 7B andthrough resistors 7-C and 7-D to high voltage positive battery. Untilrelay 7CS operates, ground is connected over a back contact of relay 7CSand the back .contact of relay 7-CH to resistor 7-D in shunt of thepositive battery, holding condenser 7B discharged. The cathode of tube7-CHT is connected over a back contact of relay 7F through the leftwinding and back contact of relay 7-CH to ground over front contacts ofrelays 76, LS1 and 762 in parallel. When relay 7-CS operates, removingthe shunt from resistor 7D, condenser 7-B starts to charge, and when thecharge reaches the breakdown potential of tube 7-CHT, that tube breaksdown, operating relay 7-CH. Relay 7-CH closes a locking circuit foritself from battery through its right winding over its own front contactto ground over front contacts of relays 7-S, 761 and 762 in parallel.Relay 7-CH, in operating, opens its operating circuit to quench tube7-CHT. Relay 7-CH closes a circuit from ground over the front contactsof relays 76, 761 and 762 in parallel, front contact of relay 7-fCH,front contact of relay 7-TC, winding of relay 7-MA to battery throughresistor 7-GA. Relay 7-MA operates and locks cverits own front contactto ground. Y

With relay 7-MA operated, ground supplied to (miti ductor 713 from theAMA equipment is connected over a front contact of relay 7-TC and thefront contact of relay 7-MA to conductor 715 causing the answer entry tobe made. When the answer entry has been completed, ground is connectedto conductor 716, completing a circuit over front contactsof relays 762,7-MA and 7-TC to resistor 7-GB in shunt of the winding ot relay 7-TC,causing relay 7-TC to release, in turn dismissing the .chargingequipment.

The release of the connection is normally under the control of thecalling subscriber. When the calling subscriber disconnects, lrelay 76releases, in turn releasing relays 761 and 762. With relay 762 released,conductors 713v and 715 are again connected together to initiate thedisconnect entry. When the disconnect entry has been completed, groundis again connected to conduc tor 716 and, with relay 762 released, thisground is extended over a back contact of relay 762, front contact ofrelay 7MA to battery through resistor 7GA in shunt of the winding ofrelay 7-MA causing the latter relay to release. The release of relays76, 761, and 762 releases relay 7-CH. The release of relay 7-MAfollowing the disconnect entry again connects ground to conductor 700and prepares the circuit for relay 7-F thereby marking the trunkavailable to the marker. The release of relay 761 also disconnects thewinding of relay 7-CS from conductors 707 and 708 to pass a disconnectsignal to the distant oice.

If the called subscriber disconnects first, the release of relay 7-CScloses a circuit from ground over the back contact ofrelay 7-CS, frontcontact of relay 7-CH, back contact of relay 7-D through the heaterwinding of thermostatic relay 7-RL. If the calling subscriberdisconnects promptly thereafter, the release of relay 7-CH opens thecircuit of relay 7-RL and disconnection takes place as above described.If the calling subscriber con tinues to hold until relay 7-RL closes itscontact, a circuit is closed from ground over the contact of relay 7-RLthrough the right winding of relay 7-D to battery. Relay 7-D, inoperating at this time, locks in a circuit from battery through itsright winding over its own front contact and the front contact of relay7-MA to ground. Re'- lay 7-D also opens the circuit of relay 7-RL topermit the heater to start cooling. Relay 7-D opens the circuit of relay761 which releases, in turn releasing relay 762. With relay 762released, the disconnect entry is made as above described except thatwith relay 7-D operated, ground is connected over the back contact ofrelay 7CS, front lcontact of relay 7-CH, which is held operated underthe control of relay 76, front contact of relay 7-D, front contact ofrelay 7-MA to conductor 717 to cause a timeout indication to be given tothe accounting equipment so that the accounting center may adjust thetime of the call for the time-out period.

In order to prevent overtime charges due to delay in obtaining access tothe charging equipment, the release of relay 761 closes a circuit fromground over back contacts of relays '761 and 7-T M and the front contactof relay 7-MA to the heater winding of the timed release relay 7-TR. Thenormal release of relay 7-MA opens the heater circuit for relay 7-TR;but, if due to delay, relay 7-TR closes its contact, it shunts relay 7MArestoring the trunk to normal without making a disconnect entry.

Relay 7-TM is operated if the trunk ,is used to set up a tandem call inwhich case the supervisory relays 76 and 7-CS do not function andcharging is performed elsewhere in the connection. Relay 7-TT is usedwhen the trunk is seized on a test call. If the sender cannot completethe connection, it operates relay 7-OF over conductor 728 to provideinterrupted tone on a subscriber call and; interrupted ground ori atandem call.

y This type et trunk is connected with the service obsex'ygA aerienne 11ing cii'uitby a number 'of conductors, including branchesof'c'oridu'ctors 712, 703, 705, 725 and 726. Conductor 7,20 is connectedto the jmake-busy conductor 727 when the trunk lis normal, andconductor'722 is connected to conductor 720 when a plug is insertedin amake-busy jack individnal to the trunk. Conductor 721 is connected to'ground when relay I'l-#C'S operates. 'Conductorr723 extends to thewinding of relay 7L-S1 and, therefore, to the operating 'and lockingcircuits for this relay. Corrductors 725 and 726 are the conductorsbywhich the sender is connected to the outgoing conductors and 708. Thelfunction of these connections betvveenvthe trunk andthe serviceobserving circuit will appear here'- inafter.

SERVICE OBSERVING EQUIPMENT Service observing trunk circuit Theoperation of the service observing connector cir-` cuit, shown in Figs.8 to 13, in interconnecting a trunk with 'the Vindividual serviceobserving circuit will be described rst. The service` observing desk isconnected with the observing equipment at the oice to be observed .bymeans of a six-conductor trunk which terminates in the service'observing trunkcircuit of Fig. 13, is connected with the serviceobserving connector circuit and is extended to one 'or the other serviceobserving circuit in accordance with the type of call to be observed. Ofthese conductors, conductors 1300 and 1301 are used initially forcarrying signals from the desk yto the service observing equipment.Conductors 1302 and 1303 are used chiefly for transmitting 'designationsto the desk while conductors 1304 and 1305 are used chiey formonitoring. All of these pairs have other functions which will appearhereinafter.

When the service observing equipment is idle, conductor 1300 isconnected 'over a back Contact of relay 13-DC, right winding ofpolarized relay 13-PB, resistors 13-Y1, and 1i3-Y, right and leftwindings Voi marginal trelay 13-ST, left winding of relay 13-PB, backcontact of relay 13-DC to conductor 1301.

Conductor 1302 is connected through the right upper winding of repeatingcoil 13-T1, b'ack contact of relay 12-ST1, right winding of marginalrelay 13-CAM, winding of` relay 13-'MA to ground, while conductor 1303is connected through the lower right winding of repeating coil 13-T1,back contact of relay 12-ST1, left winding of relay 13-CAM, resistor13-TB to battery.

Conductor 1304 extends through the upper right winding of repeating coil13-T, resistor 13-AD, left winding of polarized relay 13-D, back contactof relay 12-ST2, left winding of marginal relay 12s-FCA, back contact ofrelay 12ST2 to ground. Conductor 1305 extends through the lower rightwindingy of repeating coil 13-T, resistor 13 -AD1,back contact of relay12-ST1 to battery through resistor 13TB1 and in parallel therewiththrough the right winding of relay 13-D, back contact of relay 12-ST2,resistor 13-TG to ground.

Wit-h the observing circuits in this condition the operator at theobserving desk may set the class of observation and, if desired, may setthe trunk reduction circuit. To set the class of observation, a key isprovided at the service observing desk associated with conductors 1302'and 1303. If AMA calls to foreign areas only are to be observed, thiskey is left in its normal position and neither relay 13-CAM nor relay13-MA is operated. When AMA calls within the home area as well as callsto foreign areas are to be observed, the key at the service observingdesk is thrown to a position in which a high resistance bridge isconnected across conductors 1302 and 1303, operating relay 13-MA. Withrelay 13-MA operated, a circuit is closed from ground over a frontcontact of relay 13-MA, back contact of relay 13s-CAI, winding of relay13a-'MA1 to battery. Relay 13-MA1 operates in thiscircuit and prepares'a locking circuit for itself Vover the'tlnt contact of relay 12=ST1which becomes'effective 12 when 'the circuit is put into service. Relay13-'MA`1 is slow to release so that it remains operated after relays113-CAM and 13-MA are disconnected from trunk con- -ductors 1302 and1303 until relay 12-ST1 closes its front -contact. Relay 13-MA1 inoperating closes an obvious circuit for relay 13-HFA. If only CAMA callsare to be lobserved, the class key at the service observing desk islope'rated to a position to place 'a low resistance bridge :acrossconductors 1302 and 1303, operating both relay 13LMA and relay 13-CAM.Relay 13CAM closes an 'obvious circuit for relay 13-CA1 which prepares alocking circuit for itself under the control of relay 12-ST1 .and isalso slow to release to cover the operate time of relay 12-ST1. Relay13CA1, in turn operates relay 13-CA2 and relay 13-CA2 closes an obviouscircuit for operating relay 13-CMA. Relay 13-CA1, when operated, opensthe operating circuit for relay 13-MA1 so :that the operation of relay13-MA is ineffective under this condition. Referring to Fig. 12, it willbe seen that with relays 13-CMA and 13-HFA both deenergized,

ground is connected to conductor 1201 to cause the marker to mark AMAtrunks used in connection with foreign area lcalls for observation. Withrelay 13-HFA operated, ground is connected to conductor 1200 to causethe marker Ato mark AMA -trunks used for both home and foreign vareacalls. With relay 13CMA operated, ground is connected to conductor 1202to cause the marker to mark CAMA trunks for observation.

The trunk reduction circuit 1206 is similar to the circuit included inthe above-identified Rosene patent and is operated under the control ofa key associated with vconductors 1304 and 1305. With this key in itsnormal position, neither relay 13-D nor 13-FCA is operated and the wholegroup of trunks is subject to observation. With this key in oneott-normal position, conductors 1304 and 1305 are connected togetherdirectly and relays 13-D and 13-FCA are both operated. With this key inits other off-normal position, conductors 1304 and 1305 are connectedtogether over a high resistance bridge, causing relay 13-D to operatealone. Relay 13-D, when operated, with relay 13-ST2 normal, connectsground to conductor 1203 to cause trunk reduction circuit 1206 to selectone subgroup of trunks for observation. On the other hand, relay 13-FCAoperated with relay 12-ST2 normal connects ground to conductor 1204 toselect a different subgroup of trunks for observation. Trunk reductioncircuit 1206 is held in its set condition under the control of relay12-ST1. When the service observing desk is placed in service, a key isoperated at the desk which connects battery to conductor 1300 and groundto conductor 1301. Relays 13-ST and 13-PB operate in response to thissignal. Relay 13-'ST closes a circuit from ground over its frontcontact, back contacts of relays 12-AL and 12-AR to battery through thewinding of relay 12-ST1. Relay 12-ST1 operates and closes an obviouscircuit for operating relay 12-ST2.

Relay 12-ST1 disconnects conductors 1302 and 1303 from the classselection relays 13-CAM and 13-MA, and extends them through resistors13-AA and 13-AB toward the service observing circuits. Assuming that theclass selected is AMA, the observing circuit of Figs. 5 and 6 will beused and conductors 1302 and 1303 will be extended through the rightwindings of repeating coil 13-T1 over front contacts of relay 12-ST1through resistors 13-AA and 13-AB and conductors 1306 and 1307 to theobserving circuit of Figs. 5 and 6. A branch of conductor 1306 extendsthrough resistor 13-X and over conductor 1308 to Fig. 5.

Relay 12-ST1 also disconnects conductor 1305 from battery throughresistor 13-TB1, and with relay 12-ST2 operated, conductor 1305 extendsthrough the lower right Winding of repeating coil 13-T, resistor 13-AD1,right winding of relay 13-D, front contact `of relay 12`ST2 to conductor1309 leading to Fig. '6. Conductor 1304 'ex-

